of detroit



Filed Jan. 5. 1928 valve stem and moved Patented June 24, 1930 UNITED kSTATES PATENT OFFICE GEORGE E. A. HALLETT, OF

DETROIT, MICHIGAN, ASSIGNOR TOl GENERAL MOTORS HYDRAULIC MEcHANIsM Application led January 3, 1928*. Serial No. 244,220.

This invention relates to an improvement on the type of hydraulic gear described and claimed in my prior application, Serial No. 126,297, filed July 31st, 1926.

As in that application, there is disclosed an hydraulic chamber in which Work a plunger operated by the usual push rod reciprocated by the camshaft and hereinafter referred to as the operating plunger, and a second or operated plunger engaging the by displacement of the fluid in the chamber caused by the re- "ciprocation of the operating piston.

One of the chief difliculties encountered in the development of a device of this type is the accumulation of air in the hydraulic chamber causing noisy operationand if the amount is excessive, producing total failure of the gear. In the above application I have disclosed one Way to overcome the difficulty and in the .present case I disclose another solution embodying certain features of the first. In order to prevent the admission of air to the chamber past the sliding plungers, I have provided each plunger With a liquid seal. This may take the form of an oil filled groove surrounding the plunger and -I have preferably provided means for insuring that the groove is at all* times filled with oil, this means consisting of a connection between the groove and a suitable supply of oil.

As in my previous application, I have provided a reservoir of oil under pressure from Which the chamber is supplied with oil through a passage provided with a oneway valve and at the highest point in the chamber I have provided a vent for the discharge of air and excess oil. Instead of the special valve controlled vent disclosed in my prior case, I make use of a fixed vent, or preferably a thermally controlled vent, of the type described and claimed in the co-pending application of John O. Almen, Serial No. 241,949, filed Dec. 22, 1927. According to the present invention, I have connected the vent with the fluid reservoir so that the air and oil discharged from the chamber is returned to the reservoir and so that upon the creation of a vacuum in the chamber, as is the case When the oil contracts on cooling, oil Will be 'drawn back into the chamber through the vent. By us- 4 ing a vent of the type described `connected to a reservoir, it is possible to dispense With the maintenance of pressure in the reservoir and even with the valved inlet from the reservoir to the chamber since the reservoir may be refilled through the same passages through which air and excess oil are discharged.

The ligure is a section of my improved valve gear applied to an internal combustlon engine, a portion of the head of which is shown at 10. At 12 I have shown one of the usual poppet valves adaptedy either to admit fuel mixture to the combustion chamber or to permit the discharge of exhaust gases therefrom. The valve is normally held in seated position by springs 14 surrounding the valve stem and engaging a collar 16 carried thereby.

The member 16 is provided With a bore 18, the lower yend, of which is filled with packing 20 of cork or other suitable material to prevent the passage of oil down the valve stem into the combustion chamber. The valve stem is provided with a reduced portion 22 in which is seated a spring clip or sleeve 24 of conical shape and fitting in the bore 18 in the collar 16 for locking th collar to the stem. f

The upper end of the valve stem is apertured at 26 for the passage of a resilient pin 28, the ends of which are secured in apertures in the skirt of piston 30 reciprocating in bore 32 forming part of the hydraulic chamber 34. 36 indicates the usual camshaft operating'push rod 38 to the upper end of which is secured piston 40 working in bore 42. 44 indicates a reservoir supplied with oil or other iuid through connection 46, which may lead to the pressure lubricating system of the engine. The reservoir is provided with -spring-pressed pressure re lief valve 48. `In the system with which I have experimented I have preferred to maintain a pressure of about twent pounds per square incli in the reservoir. 'Iyhls pressure, of course` is determined by the pres- 'l' sure in the lubricating system of the :engine and the adjustment of the relief valve 48. The hydraulic chamber 34 is in communication with the reservoir 44 through passage 50 .controlled by spring-pressed valve 52.

At the highest point in the hydraulic chamber I have provided a vent 54 connected by conduit 56 to the-reservoir 44. Note that the lower end of the conduit 56 discharges adjacent the bottom of the reservoir. The vent 54 may be of the fixed type but I prefer to employ the thermally controlled vent described and claimed 1n the Almen application previously referred to. This vent consists of a tubular fitting 58 and a thermal element 60 threaded in the open end of the tting and projecting therein. The fitting 58 is rovided with seat 62 and the upper end o vthe element 60 is of conical shape to co-operate with the seat. The thermal element is of a metal such as aluminum having a higher coeliicient of ex-l pansion than the steel tting in which it is received. Consequently, as the parts be- Icome heated the thermal element will expand to a greater extent than the fitting and the vent Will' be partially or completely closed. The plungers 30 and 40` are provided with grooves 31 and 41 respectively and I have shown a tube 33 conducting oil from the reservoir..44 to the groove 31 and a pipe 43l conducting oil from the reservoir to the groove 41. By this means, the grooves are at all times maintained full ofI oil so that there is a liquid seal around the pistons preventin the entrance of air` into the hydraulic c amber. Obviously the grooves may, if preferred, be provided in the bores 32 and 42 instead of in the pistons. The p ipes 33 and43 are connected to a common fitting 64 having a tubular extension 66 which, like the extension of the conduit 56, extends belovs7 the normal level of oil in the reservoir 44. The purpose of this is to cause the extensions to be at all times sealed against the admission of air. The air collecting in the upper portion" of the chamber 44 and usually mixed with oil in the form of an emulsion `will pass outwardly through the pressure relief valve 48.

The operation is as follows:

On rotation of the camshaft 36,' the push rod 38 and piston 40 are moved upwardly exerting pressure on the fluid in the cham-.-

ber-34 causing the piston 30- to be moved outwardly unseating the valve 12. @Wing to the high ressure in the chamber 34, air and oil will discharged throu h the vent 54 and passage 56 into the cham r 44. As the vent is of very small diameter, 'the amount of oil which escapes will be so slight as to have no appreciable effect on the operation of they system. As the high part o the cam moves from beneath the push rod, the latter will b returned to its origi mea-17e The admitted oil will be free of air sinceV the passage 50 is located at the bottom ofV the reservoir. 0n the subsequent strokesof the push rod the same operation Will take place, a small portion of oil and air being discharged through the vent and a small amount of oil being admitted .by the valve 52 on the return stroke. When the parts become heated, the thermal element 60 will expand tending to close the vent and reducing the amount of oil forced out of the chamber on the operating stroke. stopped and permitted to cool down, the oil in the hydraulic chamber will contract and create a partial vacuum which, acting through conduit 56, will draw oil from the reservoir into the chamber. The liquid seals provided at 31 and 41 are always maintained by virtue of the connections with the reservoir 44 and will serve to revent the entrance of`air past the pistons into the hydraulic chamber. The reservoir 44 is supplied With oil from the engine lubricating system and to insure against the oil draining -back into the crankcase, it is usually preing, not shown, thevoil Will eventually drip down over the engine and reach the crankcase passing through the tube surrounding the valve tappets.

ll claim:

1. An hydraulic operating system comprising an hydraulic chamber, mechanism associated with the chamber for transmitting motion through pressure on the Huid therein, a fluid reservoir, and a vent of small size establishing communication between the chamber and reservoir, said vent serving at times for the discharge of air and excess oil from the chamber, and, upon contraction Aof the body of oil in the chamber, serving for the passage of oil from the reservoir to the chamber.

v2. lin the combination as defined in claim 1, means for supplying the chamber with oil under pressure.

3. ln the combination as defined in claim 1, means for supplying the chamber 'with -oill under pressure, and a valved conduit If the engine ispassage for supplying the chamber with oil from the reservoir, a passage of small size for leading air and excess oil from the chamber into the reservoir, said passage dischar ing in the reservoir below the level of oil therein so that upon contraction' of the oil in the chamber on cooling, oil is drawn into the chamber from the reservoir.

5. The combination as defined in claim 4, and means for` supplying the reservoir with oil under pressure.

6. The combination as defined in claim 4, said second-named passage connecting with vsaid chamber atv the highest point therein.

7. The combination as defined in claim 4, and thermally operated means for controlling the said second-named passage as the temperature in the chamber rises.

8. The combination of a hydraulic chamber, a plunger Working in the chamber, said plunger being provided with a liquid seal, a fluld supply passage leading to said chamber, and a'common reservoir supplying said passage and said seal.

9. The combination of a hydraulic chamber, a plunger Workingin the chamber, said plunger being provided With a liquid seal,

said chamber being' provided at its highest point with a passage for the dischar e of air, and a common reservoir for supp ying said passage and said seal.

10. The combination of a hydraulic chamber, a plunger Working in the chamber, said plunger being provided with a liquid seal to prevent the entrance of air into the chamber, a Huid passage leading to said chamber, said chamber being provided at its highest point with a passage for the discharge of air, and a common reservoir for suplplying fluid to said passages and Huid sea i l1. The combination of a hydraulic cha-mber, a plunger Working in the chamber, a

groove surrounding thev plunger, a conduit for supplying fluid-to said groove, and 'a liquid seal for the other end of the conduit. ln testimony whereof I aiiix my signature.

GEORGE E. A. HALLETT. 

